Battery life
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6zfshdb
Well-Known Member
- Region
- USA
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- Northeast Pennsylvania
Lithium batteries don't usually fail catastrophically, they slowly loose their capacity with age and use. The length of time a battery will last depends on how much capacity you need between charges. If your riding style requires 80 to 100% of capacity, if properly cared for, a general rule of thumb is 5 years for a good quality battery. However, an old battery with lesser capacity can still be useful as a spare to extend the range of your rides. Used for this purpose, it's useful life can be much longer.
I think the answer to your question will vary greatly depending on use, it's quality and how well the battery is cared for. There has been much discussion here on EBR about battery life. Try using the search function and you'll find a wealth of information on the subject.
I think the answer to your question will vary greatly depending on use, it's quality and how well the battery is cared for. There has been much discussion here on EBR about battery life. Try using the search function and you'll find a wealth of information on the subject.
Last edited:
harryS
Well-Known Member
I'm still using the 36V10AH battery I bought in 2015. Last time I did a capacity test, it gave me 9AH. To be fair, it gets light use as it's not on my daily e-rider. Maybe charged 30 times this year. Maybe 300 charges altogether in six riding seasons.
The other battery I bought in 2015 is being used by my sister on her ebike.
I did buy a battery in late 2018, and it has cheap generic chinese cells cells. It was originally rated 7.5AH and right now is only good for 4 AH before it runs out of juice. Like 6zfshdb notes, I can run it in parallel with another battery and it;s still useful.
The other battery I bought in 2015 is being used by my sister on her ebike.
I did buy a battery in late 2018, and it has cheap generic chinese cells cells. It was originally rated 7.5AH and right now is only good for 4 AH before it runs out of juice. Like 6zfshdb notes, I can run it in parallel with another battery and it;s still useful.
Sierratim
Well-Known Member
- Region
- USA
- City
- Nevada City, CA & Paradise Valley, AZ
Ah (amp-hours) is how many amperes (amps) of current a battery can deliver over a time period before it discharges. So a 10Ah battery could deliver 1amp for 10 hours, 2 amps for 5 hours, etc. Many ebike displays measure Ah for each ride. You can measure it yourself with an electrical load and a simple meter like the Powerwerx Watt meter. Incandescent lamps make good loads for battery testing.
How long can a lithium battery pack last? As others have posted, it depends on the initial quality and how the battery is 'treated'. Higher quality (read more expensive) packs will far outlast bargain batteries. Treating the battery 'gently' will also get lots more life.
More slowly charging and discharging a battery can significantly extend its life.
Limiting how much energy you draw from the battery can also dramatically extend its life.
Storage conditions play an important role as well. For longer life store batteries at ~50% charge and don't allow them to freeze.
How to translate this all to a life expectancy in years? We'll need to a set of assumptions. First, you've got a high quality battery and that 75% of original capacity is end of life as your primary battery. Also, you treat it 'gently' so you can get at least 1000 charge cycles. Finally, you ride say 100 miles/week getting ~30miles per charge. You'll be charging your battery 173 charge cycles per year. This gets you about 6 years of useful life. YRMV depending mostly on initial quality and how gentle you are willing to be.
batteryuniversity.com has a good selection of articles on these topics. Also, you can use the Search function on each of these forum pages to find several other threads on battery life and handling.
How long can a lithium battery pack last? As others have posted, it depends on the initial quality and how the battery is 'treated'. Higher quality (read more expensive) packs will far outlast bargain batteries. Treating the battery 'gently' will also get lots more life.
More slowly charging and discharging a battery can significantly extend its life.
Limiting how much energy you draw from the battery can also dramatically extend its life.
Storage conditions play an important role as well. For longer life store batteries at ~50% charge and don't allow them to freeze.
How to translate this all to a life expectancy in years? We'll need to a set of assumptions. First, you've got a high quality battery and that 75% of original capacity is end of life as your primary battery. Also, you treat it 'gently' so you can get at least 1000 charge cycles. Finally, you ride say 100 miles/week getting ~30miles per charge. You'll be charging your battery 173 charge cycles per year. This gets you about 6 years of useful life. YRMV depending mostly on initial quality and how gentle you are willing to be.
batteryuniversity.com has a good selection of articles on these topics. Also, you can use the Search function on each of these forum pages to find several other threads on battery life and handling.
Novice
Member
Thank you so much for the time you have given to your reply, I will care for my battery the very best I can, unfortunately I do not know the battery quality I received with the bike, also have no idea how to know. I really do appreciate you replying so I can stop worrying about battery life. 
Sierratim
Well-Known Member
- Region
- USA
- City
- Nevada City, CA & Paradise Valley, AZ
Lithium battery packs are rated for their nominal (50% capacity) voltages. They do require lithium specific chargers that match the battery's nominal voltage. The voltage on your charger is correct for a 36V battery. It's also identified as a Li-ion charger. Did this come with your ebike?
This chart details the voltage ranges for popular lithium battery voltages.
A 36V battery will typically range from a max of 42V at 100% charge to a min of 30V at full discharge, though full discharge is not a good idea. All modern lithium battery packs are equipped with a Battery Management System (BMS) that among other things prevents over charging and full discharging as this is not only bad for battery life but can cause overheating resulting in fires.
harryS
Well-Known Member
I use cheaper versions of the above wattmeter. They're accurate enough for me.
I splice them into the charger cable. Measure how many AH needed to recharge. I've done the converse which is to put them between the battery and the ebike, measuring how many AH came out. Numbers won't be the same because of thermodynamics, but close enough,
Once in a great while, I run a battery flat so I can measure how many AH it had, but like SierraTim notes, not something you want to do often. If you look at his chart, what I call running a battery flat still leaves some 10-15% of the charge in it.
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I splice them into the charger cable. Measure how many AH needed to recharge. I've done the converse which is to put them between the battery and the ebike, measuring how many AH came out. Numbers won't be the same because of thermodynamics, but close enough,
Once in a great while, I run a battery flat so I can measure how many AH it had, but like SierraTim notes, not something you want to do often. If you look at his chart, what I call running a battery flat still leaves some 10-15% of the charge in it.
Sierratim
Well-Known Member
- Region
- USA
- City
- Nevada City, CA & Paradise Valley, AZ
You should be good to go then.My charger chargers came with the batteries
Sierratim
Well-Known Member
- Region
- USA
- City
- Nevada City, CA & Paradise Valley, AZ
No, the charger is labeled as being a Li-ion charger at the correct voltage. The charging current at 2A max is also fairly conservative so you shouldn't have any issues.
Bruce Arnold
Well-Known Member
An unscientific observation: with reasonable care, you just might replace your ebike before you replace the battery.
Here's an example: I bought an ebike in Jan. 2018 and rode it over 4,000 miles over the next 2.5 years. While the capacity dropped some -- I could get around 60 miles if I did most of the work for the first 500 miles or so, then it plateau'ed at around 50 miles for the next 3500 miles. That means level roads, no headwind, keeping the pedal assist at a low level.
The guy who bought my bike got a good battery. He'll get thousands more miles from it.
Here's an example: I bought an ebike in Jan. 2018 and rode it over 4,000 miles over the next 2.5 years. While the capacity dropped some -- I could get around 60 miles if I did most of the work for the first 500 miles or so, then it plateau'ed at around 50 miles for the next 3500 miles. That means level roads, no headwind, keeping the pedal assist at a low level.
The guy who bought my bike got a good battery. He'll get thousands more miles from it.
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